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| United States Patent |
6,143,828
|
|
Chee
, et al.
|
November 7, 2000
|
Olefin-based crosslinked thermoplastic elastomers and a process of
preparation thereof
Abstract
There is provided olefin-based cross-linked thermoplastic elastomers and a
preparation method thereof. The TPE comprises a thermoplastic polyolefin
resin; an ethylene-propylene-dien rubber; an ethylene-octene copolymer;
and a phenolic cross-linking agent. The TPE shows good tensile strength,
tension set and compression set.
| Inventors:
|
Chee; Ho Jin (Seoul, KR);
Hwang; Min Jae (Taejeon, KR);
Lim; Byung Yun (Taejeon, KR);
Choi; Chang Hyoo (Taejeon, KR)
|
| Assignee:
|
Honam Petrochemical Corporation (Seoul, KR)
|
| Appl. No.:
|
147690 |
| Filed:
|
February 16, 1999 |
| PCT Filed:
|
June 14, 1997
|
| PCT NO:
|
PCT/KR97/00114
|
| 371 Date:
|
February 16, 1999
|
| 102(e) Date:
|
February 16, 1999
|
| PCT PUB.NO.:
|
WO98/58020 |
| PCT PUB. Date:
|
December 23, 1998 |
| Current U.S. Class: |
525/192; 525/194; 525/195; 525/240; 525/241 |
| Intern'l Class: |
C08F 008/00; C08L 025/00; C08L 025/02 |
| Field of Search: |
525/192,194,195,240,241
|
References Cited
U.S. Patent Documents
| 3758643 | Sep., 1973 | Fischer.
| |
| 4311628 | Jan., 1982 | Abdou-Sabet et al.
| |
| 4785045 | Nov., 1988 | Yonekura et al. | 524/528.
|
| 5272236 | Dec., 1993 | Lai et al. | 526/348.
|
| 5278272 | Jan., 1994 | Lai et al. | 526/348.
|
| 5389715 | Feb., 1995 | Davis et al. | 524/505.
|
| 5717020 | Feb., 1998 | Kopytko | 524/425.
|
| Foreign Patent Documents |
| 213 285 | Mar., 1987 | EP.
| |
| 256 724 | Feb., 1988 | EP.
| |
| 519 691 | Dec., 1992 | EP.
| |
Primary Examiner: Nutter; Nathan M.
Attorney, Agent or Firm: Foley & Lardner
Parent Case Text
This application claims the benefit under 35 USC 371 of prior PCT
International Application No. PCT/KR97/00114 which has an International
filing date of Jun. 14, 1997.
Claims
What is claimed is:
1. An olefin-based crosslinked thermoplastic elastomer comprising, based on
100 parts by weight of following (A)+(B)+(C),
(A) 17-82 parts by weight of a thermoplastic polyolefin resin;
(B) 14.2-76 parts by weight of an ethylene-propylene-diene rubber which
satisfies the following conditions;
(a) propylene content: 10-50 wt %
(b) Mooney viscosity at 100.degree. C.: 20-100 ML.sub.1+4
(C) 3.8-76 parts by weight of an ethylene-octene copolymer which satisfies
the following conditions;
(a) octene content: 9.5-30 wt %
(b) melt index: 0.3-30 dg/min.; and
(D) 1-15 parts by weight of a phenolic crosslinking agent.
2. The olefin-based crosslinked thermoplastic elastomer according to claim
1, which comprises, based on 100 parts by weight of following (A)+(B)+(C),
(A) 20-70 parts by weight of a thermoplastic polyolefin resin;
(B) 30-60 parts by weight of an ethylene-propylene-diene rubber which
satisfies the following conditions;
(a) propylene content: 10-50 wt %
(b) Mooney viscosity at 100.degree. C.: 20-100 ML.sub.1+4
(C) 20-50 parts by weight of an ethylene-octene copolymer which satisfies
the following conditions;
(a) octene content: 9.5-30 wt %
(b) melt index: 0.3-30 dg/min.; and
(D) 3-15 parts by weight of a phenolic crosslinking agent.
3. The olefin-based crosslinked thermoplastic elastomer according to claim
1 or 2, wherein said ethylene-octene copolymer is obtained by
copolymerizing ethylene units with octene in the presence of metallocene
catalyst.
4. The olefin-based crosslinked thermoplastic elastomer according to claim
1 or 2, wherein said polyolefin thermoplastic resin(A) is
homopolypropylene or, lock or random copolymers of ethylene and propylene.
5. The olefin-based crosslinked thermoplastic elastomer according to claim
1 or 2, wherein said the phenolic crosslinking agent is dimethylol
phenolic resins.
6. The olefin-based crosslinked thermoplastic elastomer according to claim
1 or 2, which further comprises one or more crosslinking accelerators
selected from a group consisting of oxides of Mg, Pb and Zn in an amount
of 1-7 parts by weight based on 100 parts by weight of (A)+(B)+(C).
7. A method for preparing an olefin-based crosslinked thermoplastic
elastomer, which comprises step of dynamical vulcanization following
components (A)-(D) at a temperature of 170-220.degree. C., 30-120 rpm
during retention time of 5-20 minutes,
(A) 17-82 parts by weight of a thermoplastic polyolefin resin;
(B) 14.2-76 parts by weight of an ethylene-propylene-diene rubber which
satisfies the following conditions;
(a) propylene content: 10-50 wt %
(b) Mooney viscosity at 100.degree. C.: 20-100 ML.sub.1+4
(C) 3.8-76 parts by weight of an ethylene-octene copolymer which satisfies
the following conditions;
(a) octene content: 9.5-30 wt %
(b) melt index: 0.3-30 dg/min.; and
(D) 1-15 parts by weight of a phenolic crosslinking agent, wherein said
parts by weight being based on 100 parts by weight of (A)+(B)+(C).
8. The method according to claim 7, wherein said ethylene-octene copolymer
is obtained by copolymerizing ethylene units with octene in the presence
of metallocene catalyst.
9. The method according to claim 7, wherein one or more crosslinking
accelerators selected from a group consisting of oxides of Mg, Pb and Zn
in an amount of 1-7 parts by weight based on 100 parts by weight of
(A)+(B)+(C) are incorporated.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to olefin-based crosslinked
thermoplastic elastomers and a process of preparation thereof. More
particularly, the present invention relates to olefin-based crosslinked
thermoplastic elastomers made from an olefin-based resin, an
ethylene-propylene-diene rubber and an ethylene-octene copolymer and
having improved properties, and to a process of preparation thereof.
2. Description of the Related Arts
Olefin-based thermoplastic resins modified with elastomers such as rubbers
to impart elasticity, or elastomers modified with thermoplastic resins to
render having processability are extensively developed due to their good
physical properties and good processability. These types of materials are
designated as thermoplastic elastomers because they exhibit
thermoplasticity as well as elasticity. They are advantageous in that they
can be directly molded by using extrusion, injection and press molding
process without crosslinking-aging step, which is required for common
rubber to be molded. For this reason, they replace a wide range of rubbers
needing processability and thermoplastic resins needing elasticity. In
particular, olefin-based crosslinked thermoplastic elastomers, unlike
styrene-based copolymers or urethane-based thermoplastic elastomers, show
a wide range of physical and processing characteristics depending on the
degree of crosslinking of elastomers incorporated therein. This renders
them applicable to a wide range of uses and have highest market share.
Various researches have been made to develop new crosslinking systems
which can be advantageously used for olefin-based crosslinked elastomers
having a same composition. in general, crosslinked thermoplastic
elastomers are classified into three groups: no cured thermoplastic
elastomer (hereinafter referred to as TPO) wherein rubbers are
incorporated without a crosslinking agent; partially crosslinked
thermoplastic elastomers (hereinafter referred to as TPR) wherein rubbers
are partially crosslinked into the thermoplastic resin; and completely
crosslinked thermoplastic elastomers (hereinafter referred to as TPV)
wherein rubbers are completely crosslinked into the thermoplastic resin.
The degree of crosslinking affects the size and fine dispersion of rubber
particles in crosslinked thermoplastic elastomers, consequently affects
elastic characteristics such as tensile strength, permanent tension set,
permanent compression set and et al. In more detail, in cases of TPO
having no crosslinking of rubber and TPR, there are limitations in
obtaining the finely dispersed rubber particles by shear stress.
Especially, this becomes more severe as the amount of rubber increases.
For this reason, materials requiring elasticity and thermoplasticity
should have been made by the dynamic vulcanization in which cured rubbers
are pulverized by shear stress during the mixing.
Many developments have been made for crosslinked thermoplastic elastomers.
For example, commercial olefin-based crosslinked TPE may include TPR.TM.
by UniRoyal, USA (U.S. Pat. No. 3,758,643), which is the first commercial
product, and Santoprene.TM. by Monsanto, USA (U.S. Pat. No. 4,311,628). As
crosslinked thermoplastic elastomers using peroxides as a crosslinking
agent, Milastomer.TM. by Mitsui Petrochemical, Japan (U.S. Pat. No.
4,785,045).
TPR.TM. and Milastomer.TM. are crosslinked hermoplastic elastomers in which
a combination of polyolefin resin and ethylene-propylene rubber
(hereinafter referred to as EPR), or of ethylene-propylene-diene rubber
(hereinafter referred to as EPDM) is partially crosslinked by using
peroxide crosslinking agents. When peroxide crosslinking agents are used
for the crosslinking of rubbers, crosslinking rate and reactivity are
good. On the other hand, peroxide crosslinking agents can not be used in a
sufficient amount, since polyolefin is decomposed by the crosslinking
agents. Therefore, there is a limitation in improving the elastic
characteristics such as permanent compression set or permanent tension
set. Moreover, because the decomposition of polyolefin resin is induced
during the crosslinking of rubbers goes on, mechanical properties and
stability of system are deteriorated.
Santoprene.TM. is a crosslinked thermoplastic elastomer by completely
crosslinking a combination of polyolefin and EPDM using a phenolic
crosslinking agent. Since a tin-based crosslinking accelerator is used to
increase the rate of crosslinking, the final product has odor and brownish
color, and is apt to absorb moisture. Although the degree of crosslinking
can be increased since only EPDM rubber is used, the remaining
crosslinking agent may cause a excessive crosslinking during molding
process, consequently the mechanical properties such as tensile strength
and elongation, and permanent compression set are decreased.
Accordingly, olefin-based crosslinked thermoplastic elastomers free from
the problems of the conventional TPE has been needed.
SUMMARY OF THE INVENTION
Thus, the present invention provides olefin-based crosslinked thermoplastic
elastomers having good elasticity.
The present invention also provides a new crosslinking agent system.
The present invention still provides olefin-based crosslinked thermoplastic
elastomers having good tensile strength and good elastic properties such
as permanent compression set and permanent tension set.
Further, the present invention provides a method for preparing olefin-based
crosslinked thermoplastic elastomers.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is based on the findings that partially crosslinked
thermoplastic elastomers can show better tensile strength and good elastic
properties such as permanent compression set and permanent tension set
than those of completely crosslinked thermoplastic elastomers, when the
smaller size and finer dispersion of the rubber particles in the system is
obtained from the reduction of the difference of interfacial tension and
the increase of interfacial adhesion between the components in a
multi-component system at the early stage of dynamic vulcanization
process.
Thus, a mixture of a conventional polypropylene thermoplastic resin (First
component) and ethylene-propylene-diene rubber (Second component) is
combined with ethylene-octene copolymer (Third component) to improve
interfacial adhesions, which consequently renders a production of
olefin-based crosslinked thermoplastic elastomers having good properties.
Ethylene of the third component is the same as ethylene of the second
component.
According to the present invention, the partially crosslinked third
component can be obtained by using a proper crosslinking agent system. By
using the crosslinking agent system according to the present invention,
the degree of crosslinking and consequently the density of crosslinking
can be improved. Thus, it can be crosslinked thermoplastic elastomers
showing improved tensile strength and good elastic properties such as
permanent compression set and permanent tension set.
The olefin-based crosslinked thermoplastic elastomer (hereinafter referred
to as `TPE`) comprises an olefin-based thermoplastic resin and an
olefin-based rubber, and further comprises ethylene-octene copolymer
wherein ethylene units are copolymerized with octene in the presence of a
metallocene catalyst.
The TPE according to the present invention comprises, based on 100 parts by
weight of following (A)+(B)+(C),
(A) 17-82 parts by weight of a thermoplastic polyolefin resin;
(B) 14.2-76 parts by weight of an ethylene-propylene-diene rubber
satisfying the following conditions;
(a) propylene content: 10-50 wt %
(b) Mooney viscosity at 100.degree. C.: 20-100 ML.sub.1+4
(C) 3.8-76 parts by weight of an ethylene-octene copolymer in which
ethylene units are copolymerized with octene in the presence of
metallocene catalyst and which satisfies the following conditions;
(a) octene content: 9.5-30 wt %
(b) melt index: 0.3-30 dg/min.; and
(D) 1-15 parts by weight of a phenolic crosslinking agent.
Each component of the elastomer will be described in detail below.
As a thermoplastic polyolefin resin (A), homopolypropylene or, block or
random copolymers of ethylene and propylene may be used. When the amount
of the resin (A) is less than 17 parts by weight with respect to 100 parts
by weight of the total amount of (A), (B) and (C), the mechanical strength
and processability of the resulting TPE are deteriorated. On the other
hand, when the amount of the resin (A) exceeds 82 parts by weight, impact
strength and elasticity of the resulting elastomer are deteriorated.
Therefore, according to the present invention, the polyolefin resin (A) is
used in an amount of 17-82 parts by weight, preferably 20-70 parts by
weight based on 100 parts by weight of (A)+(B)+(C).
Ethylene-propylene-diene rubber (`EPDM`) (B) of the present invention has
been incorporated into crosslinked thermoplastic elastomer as frequently
as ethylene-propylene rubber, since EPDM (B) exhibits good compatibility
with the resin (A), and better ozone-proof and weatherability than other
rubbers such as natural, styrene-butadiene, chloroprene and nitrile-based
rubbers. Further, EPDM is advantageous that it can be crosslinked by
phenolic crosslinking agents, since it has unsaturated bonds between
carbon atoms.
For the present invention, 14.2-76 parts by weight, preferably 30-60 parts
by weight, based on 100 parts by weight of (A)+(B)+(C), of EPDM is used
and EPDM has a propylene content of 10-50 wt % and Mooney viscosity at
100.degree. C. of 20-100 ML.sub.1+4. When the Mooney viscosity at
100.degree. C. is less than 20 ML.sub.1+4, mechanical strength of the
resulting TPE is deteriorated and dispersive rearrangement by shear stress
is not satisfactory. On the other hand, when the Mooney viscosity at
100.degree. C. exceeds 100 ML.sub.1+4, the processability of the TPE is
deteriorated.
Ethylene-octene copolymer (`EOR`) (C) is an ethylene-based rubber in which
octene is copolymerized as a long branch chain, and is used to increase
elasticity of the TPE due to the increased interfacial adhesion of the
system. EOR (C) has an octene content of 9.5-30 wt %. Since EOR having the
octene content more than 10 wt % cannot be obtained by using Ziegler-Natta
catalyst, EOR prepared by using metallocene catalyst is used. The
preparation of EOR having the octene content of 9.5-30 wt % using
metallocene catalyst is described in, for example U.S. Pat. No. 5,272,236
and U.S. Pat. No. 5,278,272.
EOR (C) shows good compatibility with EPDM (B) due to ethylene component,
and has a narrow molecular weight distribution and uniform physical
properties. Further, EOR (C) exhibits greater heat-resistance and
photo-resistance than other rubbers, due to the presence of octene unit.
Thus, a long branch chain with the octene component imparts gloss and
clearness to the TPE, and contributes good processability to the TPE. For
the present invention, EOR (C) is used in the amount of 3.8-76 parts by
weight, preferably 20-50 parts by weight based on 100 parts by weight of
(A)+(B)+(C). When the amount of EOR (C) exceeds 76 parts by weight, the
density of crosslinking is reduced and consequently elasticity of the TPE
is decreased.
According to the present invention, a phenolic resin is used as a
crosslinking agent. In particular, dimethylol phenolic resins may
advantageously be used. The phenolic resin proceeds with crosslinking
process by decomposing unsaturated carbon bonds in EPDM (B), and can be
used to sufficient amount since it does not decompose polyolefin resin
(A), unlike peroxide crosslinking agent. This enables the degree of
crosslinking as wide as from 10% to 95%. For the present invention,
phenolic resin (D) is used in the amount of 1-15 parts by weight,
preferably 3-15 parts by weight based on 100 parts by weight of
(A)+(B)+(C). When the amount of phenolic resin (D) exceeds 15 parts by
weight, the remaining crosslinking agent (D) after the crosslinking
process will proceed with further crosslinking during the subsequent
molding process, eventually resulting in a deterioration of physical
properties of the molded articles.
According to the present invention, a crosslinking accelerator may be used
to increase the rate of crosslinking. The crosslinking accelerator, which
may be used for the present invention, may include oxides of Mg, Pb or Zn,
in single or combinations thereof. The crosslinking accelerator may be
used in the amount of 1-7 parts by weight based on 100 parts by weight of
(A)+(B)+(C).
The crosslinking agent system according to the invention, which is
comprised of a phenolic resin (D) and a metal oxide, can induce a
crosslinking of EOR so that it can effectively improve the degree of
crosslinking compared when only phenolic resin (D) is used. Further, it
can block an excessive crosslinking during the molding process to maintain
the mechanical properties of the TPE stably.
The TPE may be further incorporated with additives which are commonly used
in the resin composition to improve the physical properties of the TPE.
The additives may include, but not limited thereto, inorganic additives
such as silica, clay, talc, titanium oxide, zinc oxide or lead oxide,
carbon black, flame retardants, thermostabilizers and the like.
The TPE according to the present invention may be prepared by subjecting
the composition containing the components described above to dynamic
vulcanization process at a temperature of 170-220.degree. C., 30-120 rpm
during the retention time of 5-20 minutes.
PREFERRED EMBODIMENTS OF THE INVENTION
The present invention will be described in more detail by way of the
following Examples, which should not be considered to limit the scope of
the present invention.
EXAMPLE 1
40 parts by weight of polypropylene(isotactic index: 98%, melt index: 10
dg/min), 50 parts by weight of EPDM(l)(propylene content: 43%, Mooney
viscosity: 65 ML.sub.1+4 (100.degree. C.)), 10 parts by weight of
EOR(l)(octene content: 24%, melt index: 1 dg/min), 1 parts by weight of
dimethylol phenolic resin, 1 parts by weight of crosslinking accelerator
A(oxides of Mg), 7 parts by weight of organic additives and proper
quantity of other additives such as antioxidant, antistatic agent and
thermostabilizer were mixed in a plasti-corder (mixer for intensive
mixing), and dynamic vulcanization process was performed under a condition
of 200.degree. C. and 100 rpm, during the retention time of 5 minutes.
Then, the mixture was dried in an oven of 120.degree. C. for about 2
hours. Test specimens were prepared from injection molding.
In order to evaluate the properties of the resulting crosslinked TPE,
mechanical properties(stress-strain) was measured according to the method
of ASTM D-412 and D-624, surface hardness was according to the method of
D-2240, permanent compression set was according to the method of D-395.
These methods have been applied for the conventional crosslinked
thermoplastic elastomers. Further, to measure the degree of crosslinking,
test specimen was pulverized and then 30 g of the powder was placed in a
boiling xylene for 12 hours. The degree of crosslinking was defined as
weight of the remaining samples. The results are shown in Table 1.
EXAMPLES 2.about.12
By following the procedure of Example 1, crosslinked thermoplastic
elastomers were prepared, except that the amount of crosslinking agent,
and kind and amount of crosslinking accelerator are selected as shown in
Table 1. The properties of the products were measured by the same criteria
and methods in Example 1, and the results are shown in Table 1.
TABLE 1
__________________________________________________________________________
Examples
Components 1 2 3 4 5 6 7 8 9 10 11 12
__________________________________________________________________________
EPDM(1) 50 50 50 50 50 50 50 50 50 50 50 50
EOR(1) 10 10 10 10 10 10 10 10 10 10 10 10
Polypropylene 40 40 40 40 40 40 40 40 40 40 40 40
Crosslinking agent 1 1 1 3 3 3 5 5 5 5 7 7
Crosslinking accelerator A 1 -- -- -- 2 2 -- 3 2 2 3 --
Crosslinking accelerator B -- 1 -- -- 1 -- -- -- 1 -- -- 2
Crosslinking accelerator C -- -- 1 -- -- 1 -- -- -- 1 -- 1
__________________________________________________________________________
Properties
ASTM
Units
Temp.
__________________________________________________________________________
Hardness D2240 shore 25.degree. C. 75A 72A 75A 78A 80A 81A 80A 83A 83A
85A 83A 84A
Tensile D412 kgf/cm.sup.2 25.degree. C. 67 63 69 71 75 77 85 90 90 93
91 94
strength
100% D412 kgf/cm.sup.2 25.degree. C. 61 59 60 63 66 68 72 76 78 78 78
79
Modulus
Elongation D412 % 25.degree. C. 500 500 500 480 450 430 400 370 380 360
320 300
Crosslinking Xylene wt % Boil 25 20 21 35 40 43 53 60 61 63 62 63
degree
__________________________________________________________________________
(Note)
(a) EPDM(1): ethylene-propylene-diene rubber
propylene content: 43%; Mooney viscosity: 65 ML.sub.1+4 (100.degree. C.)
(b) EOR(1): ethylene-octene copolymer
octene content: 24%; melt index: 1 dg/min
(c) Polypropylene: manufactured by Honam Petrochemical Corp.
melt index: 10 dg/min; isotactic index: 98%
(d) Crosslinking agent: Dimethylol phenolic resin
(e) Crosslinking accelerator A: Oxides of Mg
(f) Crosslinking accelerator B: Oxides of Pb
(g) Crosslinking accelerator C: Oxides of Zn
EXAMPLES 13.about.24
By following the procedure of Example 1, crosslinked thermoplastic
elastomers were prepared, except that the amounts of polypropylene, EPDM,
EOR and the crosslinking agent, and kind and amount of crosslinking
accelerator are selected as shown in Table 2. The properties of the
products were measured by the same criteria and methods in Example 1, and
the results are shown in Table 2.
TABLE 2
__________________________________________________________________________
Examples
Components 13 14 15 16 17 18 19 20 21 22 23 24
__________________________________________________________________________
EPDM(1) 60 60 60 60 60 60 60 60 60 60 60 60
EOR(1) 12 12 12 12 12 12 12 12 12 12 12 12
Polypropylene 28 28 28 28 28 28 28 28 28 28 28 28
Crosslinking agent 5 5 5 5 7 7 7 7 9 9 12 15
Crosslinking accelerator A -- 3 -- -- -- 4 4 5 7 7 5 --
Crosslinking accelerator B -- -- 3 -- -- 1 -- -- 3 -- 5 5
Crosslinking accelerator C -- -- -- 3 -- -- 1 -- -- 3 -- 5
__________________________________________________________________________
Properties
ASTM
Units
Temp.
__________________________________________________________________________
Hardness D2240 shore 25.degree. C. 62A 64A 64A 64A 64A 66A 68A 66A 68A
68A 68A 70A
Tensile D412 kgf/cm.sup.2 25.degree. C. 42 48 48 49 49 57 58 55 62 65
66 68
strength
100% D412 kgf/cm.sup.2 25.degree. C. 30 38 35 37 35 41 44 39 44 46 46
47
Modulus
Elongation D412 % 25.degree. C. 500 450 450 450 410 380 360 400 340 300
280 220
Permanent D412 % 25.degree. C. 18 15 16 15 15 14 13 14 12 11 10 10
tension set
Permanent D395 % 70.degree. C. 39 34 35 33 34 30 29 32 30 28 28 27
compression
set
Crosslinking Xylene wt % Boil 34 43 40 44 50 57 59 55 72 74 74 75
degree
__________________________________________________________________________
(Note)
(a) EPDM(1): ethylene-propylene-diene rubber
propylene content: 43%; Mooney viscosity: 65 ML.sub.1+4 (100.degree. C.)
(b) EOR(1): ethylene-octene copolymer
octene content: 24%; melt index: 1 dg/min
(c) Polypropylene: manufactured by Honam Petrochemical Corp.
melt index 10 dg/min; isotactic index: 98%
(d) Crosslinking agent: Dimethylol phenolic resin
(e) Crosslinking accelerator A: Oxides of Mg
(f) Crosslinking accelerator B: Oxides of Pb
(g) Crosslinking accelerator C: Oxides of Zn
As shown in Tables 1 and 2, the present invention can provide crosslinked
thermoplastic elastomers having various hardnesses and therein good
properties. Also, the degree of crosslinking can be increased by using
phenolic resin together with crosslinking accelerator of metal oxides, and
in these cases the products have prefer properties to the product prepared
by using only phenolic resin. Further, among the crosslinking agent
systems, system consisting of phenolic resin, oxides of Mg and oxides of
Zn is the most effective.
EXAMPLES 25.about.32 AND COMPARATIVE EXAMPLES 1.about.2
By following the procedure of Example 1, crosslinked thermoplastic
elastomers were prepared, except that the amounts of polypropylene and the
crosslinking agent, and kinds and amounts of EPDM, EOR and crosslinking
accelerator are selected as shown in Table 3. The properties of the
products were measured by the same criteria and methods in Example 1, and
the results are shown in Table 3.
TABLE 3
__________________________________________________________________________
Comp. Comp.
Example Example Example
Components 1 25 26 27 28 29 30 31 32 2
__________________________________________________________________________
EPDM(2) 76 56 56 56 66 46 36 26 16 --
EOR(2) -- 20 -- -- -- -- -- -- -- --
EOR(3) -- -- 20 -- 10 30 40 50 60 76
EOR(4) -- -- -- 20 -- -- -- -- -- --
Polypropylene 24 24 24 24 24 24 24 24 24 24
Crosslinking agent 12 12 12 12 12 12 12 12 12 12
Crosslinking accelerator A 4 4 4 4 4 4 4 4 4 4
Crosslinking accelerator B 2 2 2 2 2 2 2 2 2 2
__________________________________________________________________________
Properties
ASTM
Units
Temp.
__________________________________________________________________________
Hardness D2240 shore 25.degree. C. 63A 66A 66A 66A 64A 70A 85A 40D 50D
60D
Tensile D412 kgf/cm.sup.2 25.degree. C. 55 58 65 70 60 71 62 48 55 65
strength
100% D12 kgf/cm.sup.2 25.degree. C. 41 47 56 59 52 59 47 25 30 31
Modulus
Permanent D412 % 25.degree. C. 12 10 9 9 11 8 12 25 -- --
tension set
Permanent D395 % 70.degree. C. 28 25 23 23 25 23 27 35 -- --
compression
set
Crosslinking Xylene wt % Boil 83 68 71 70 75 61 49 44 30 12
degree
__________________________________________________________________________
(Note)
(a) EPDM(2): ethylene-propylene-diene rubber
propylene content: 35%; Mooney viscosity 69 ML.sub.1+4 (100.degree. C.)
(b) EOR(2): ethylene-octene copolymer
octene content: 30%; melt index: 0.3 dg/min
(c) EOR(3): ethylene-octene copolymer
octene content: 20%; melt index: 18 dg/min
(d) EOR(4): ethylene-octene copolymer
octene content: 9.5%; melt index: 30 dg/min
(e) Polypropylene: manufactured by Honam Petrochemical Corp.
melt index: 10 dg/min; isotactic index: 98%
(f) Crosslinking agent: Dimethylol phenolic resin
(g) Crosslinking accelerator A: Oxides of Mg
(h) Crosslinking accelerator B: Oxides of Pb
The results of Table 3 show that apart from EPDM, some amount of EOR may
also be crosslinked by using the crosslinking agent system according to
the present. That is to say, the crosslinking system with metal oxides may
induce the crosslinking reaction of EOR, and thereby the degree of
crosslinking can be increased. This shows that, within the same amount of
rubber, the crosslinked thermoplastic elastomers prepared by using EOR
together with EPDM have better properties than those prepared by using
only EPDM. But, the crosslinked thermoplastic elastomer prepared by using
only EOR(the product of Comp. Example 2) has poor properties due to the
low degree of crosslinking.
EXAMPLES 33.about.43
Examples 33.about.43 are provided for illustrating the properties of the
crosslinked thermoplastic elastomers prepared by varying the kind of EPDM.
By following the procedure of Example 1, crosslinked thermoplastic
elastomers were prepared, except that the amounts of polypropylene, EOR,
the crosslinking agent and the crosslinking accelerator, and kind and
amount of EPDM are selected as shown in Table 4. The properties of the
products were measured by the same criteria and methods in Example 1 and
the results are shown in Table 4.
TABLE 4
__________________________________________________________________________
Examples
Components 33 34 35 36 37 38 39 40 41 42 43
__________________________________________________________________________
EPDM(3) 65.6 60 -- -- -- 51.3 42.7 34 26.1 17.4 14.2
EPDM(4) -- -- 60 -- -- -- -- -- -- -- --
EPDM(5) -- -- -- 60 -- -- -- -- -- -- --
EPDM(6) -- -- -- -- 60 -- -- -- -- -- --
EOR(1) 17.4 16 16 16 16 13.7 11.3 9 6.9 4.6 3.8
Polypropylene 17 24 24 24 24 35 46 57 68 78 82
Crosslinking agent 7.6 7 7 7 7 6 5 4 3 2 1.7
Crosslinking accelerator A 5.5 5 5 5 5 4.3 3.6 2.8 2.2 1.5 1.2
__________________________________________________________________________
Properties
ASTM
Units
Temp.
__________________________________________________________________________
Hardness D2240 shore 25.degree. C. 56A 64A 62A 62A 60A 70A 78A 86A 43D
50D 55D
Tensile D412 kgf/cm.sup.2 25.degree. C. 46 55 53 53 50 70 78 110 180
230 260
strength
100% D412 kgf/cm.sup.2 25.degree. C. 37 42 40 40 36 47 53 85 120 160
180
Modulus
Elongation D412 % 25.degree. C. 220 270 300 300 320 320 330 420 530 580
600
Permanent D412 % 25.degree. c. 8 12 13 13 14 13 16 23 42 48 --
tension set
Permanent D395 % 70.degree. C. 25 29 30 30 32 30 32 38 45 -- --
compression
set
Crosslinking Xylene wt % Boil 79 73 69 68 65 64 55 46 39 30 27
degree
__________________________________________________________________________
(Note)
(a) EPDM(3): ethylene-propylene-diene rubber
propylene content: 15%; Mooney viscosity: 72 ML.sub.1+4 (100.degree. C.)
(b) EPDM(4): ethylene-propylene-diene rubber
propylene content: 25%; Mooney viscosity: 50 ML.sub.1+4 (100.degree. C.)
(c) EPDM(5): ethylene-propylene-diene rubber
propylene content: 37%; Mooney viscosity: 20 ML.sub.1+4 (100.degree. C.)
(d) EPDM(6): ethylene-propylene-diene rubber
propylene content: 46%; Mooney viscosity: 100 ML.sub.1+4 (100.degree. C.)
(e) EOR(1): ethylene-octene copolymer
octene content: 24%; melt index: 1 dg/min
(f) Polypropylene: manufactured by Honam Petrochemical Corp.
melt index: 10 dg/min; isotactic index: 98%
(g) Crosslinking agent: Dimethylol phenolic resin
(e) Crosslinking accelerator A: Oxides of Mg
EXAMPLES 44.about.46 AND COMPARATIVE EXAMPLES 3.about.11
By following the procedure of Example 1, crosslinked thermoplastic 10
elastomers were prepared, except that the amounts of polypropylene and the
crosslinking agent, and kinds and amounts of EPDM, EOR and crosslinking
accelerator are selected as shown in Table 5. The properties of the
products were measured by the same criteria and methods in Example 1, and
the results are shown in Table 5.
TABLE 5
__________________________________________________________________________
C. Ex.
Ex.
C. Ex. Ex.
C. Ex. Ex.
C. Ex.
Components 3 44 4 5 6 45 7 8 9 46 10 11
__________________________________________________________________________
EPDM(4) 76 56 56 56 59 39 39 39 42 30 30 30
EOR(5) -- 20 -- 10 -- 20 -- 10 -- 12 -- 6
Styrene-butadien rubber -- -- 20 10 -- -- 20 10 -- -- 12 6
Polypropylene 24 24 24 24 41 41 41 41 58 58 58 58
Crosslinking agent 9 9 9 9 7 7 7 7 5 5 5 5
Crosslinking accelerator A 3 3 3 3 4 4 4 4 4 4 4 4
Crosslinking accelerator B 2 2 2 2 2 2 2 2 1 1 1 1
__________________________________________________________________________
Properties
ASTM
Units
Temp.
__________________________________________________________________________
Hardness D2240 shore 25.degree. C. 65A 66A 64A 65A 73A 75A 72A 73A 82A
84A 81A 82A
Tensile D412 kgf/cm.sup.2 25.degree. C. 53 56 48 48 74 79 68 70 87 91
83 85
strength
100% D412 kgf/cm.sup.2 25.degree. C. 40 44 35 36 50 55 46 50 58 62 50
54
Modulus
Permanent D412 % 25.degree. C. 13 11 14 14 15 14 17 16 17 15 18 18
tension set
Permanent D395 % 70.degree. C. 29 27 31 32 32 30 34 33 34 32 36 35
compression
set
Crosslinking Xylene wt % Boil 83 72 62 66 65 55 46 50 49 44 36 41
degree
__________________________________________________________________________
(Note)
(a) EPDM(4): ethylene-propylene-diene rubber
propylene content: 25%; Mooney viscosity: 50 ML.sub.1+4 (100.degree. C.)
(b) EOR(5): ethylene-octene copolymer
octene content: 19%; melt index: 30 dg/min
(c) Styrene-butadiene rubber: styrene content: 23%
(d) Polypropylene: manufactured by Honam Petrochemical Corp.
melt index: 10 dg/min; isotactic index: 98%
(e) Crosslinking agent: Dimethylol phenolic resin
(f) Crosslinking accelerator A: Oxides of Mg
(g) Crosslinking accelerator B: Oxides of Pb
As shown in Table 5, the crosslinked thermoplastic elastomers prepared by
using styrene-butadien rubber(SBR) together with EPDM have inferior
properties to the products prepared by using only EPDM or using EOR and
EPDM. This indicates that SBR is not crosslinked by the crosslinking agent
system according to the present, and that the interfacial adhesions
between SBR and EPDM or polypropylene are weak.
As above described, according to the present invention, ethylene-octene
copolymer incorporated in the crosslinking system comprising olefin-based
thermoplastic resin and olefin-based rubber may be partially crosslinked
by the crosslinking agent system consisting of phenolic resin and metal
oxides and exist in the form of fine and uniform dispersion. Further, the
interfacial adhesion between the ethylene-octene copolymer and the
crosslinked ethylene-propylene-dien rubber can increase the degree of
crosslinking. Consequently, the crosslinked thermoplastic elastomers
provided by the present invention have good properties such as the tensile
strength, tension set, compression set and the like.
Although preferred embodiments of the present invention have been described
in detail hereinabove, it should be clearly understood that many
variations and/or modifications of the basic inventive concepts herein
taught which may appear to those skilled in the art will still fall within
the spirit and scope of the present invention as defined in the appended
claims.
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